Electric current-voltage converting circuit



United States Patent inventors ShinichiroOgawa;

Toshiyuki Matsuda, Tokyo, Japan Appl. No. 759,908 I. Filed Sept. 16, 1968 Patented Dec. 22, 1970 Assignee Honeywell Inc.

Minneapolis, Minn.

a corporation of Delaware Priority Sept. 18, 1967 Japan ELECTRIC CURRENT-VOLTAGECONVERTING CIRCUIT 1 Claim, 5 Drawing Figs.

U.S. Cl. 307/270, 307/297. 307/3 l3: 323/4: 330/17. 330/24 Int. Cl. H031: 3/26 Field ofSearch 307/270,

References Cited UNITED STATES PATENTS 3,271.528 9/1966 Vallese 330/30 3,383,612 5/1968 Harwood.... 330/22 3,438,028 4/1969 Stewart 330/17X Primary Examiner-Donald D. Forrer Assistant ExaminerR. C. Woodbridge AttorneysArthur H. Swanson and Lockwood D. Burton ABSTRACT: A first serial connection. comprises a first resistor, a first composite transistor and a first load. A second serial connection comprises a second load, a second composite transistor, a second resistor, a third load and a third resistor which is connected in the circuit of the second composite transistor. An output voltage of a magnitude larger than the magnitude of the voltage drop due to an input current is obtained.

PATENTEnniczzlem 35491910 INVENTOR s. SHINICHIRO OGAWA BY TO IYUKI MATSUDA ATTORNEY ELECTRIC CURRENT-VOLTAGE CONVERTING CIRCUIT BACKGROUND OF THE INVENTION This invention relates to a current-voltage converting circuit and more particularly to a current-voltage converting cir cuit in which a resistor is inserted in a composite transistor circuit used for this current-voltage converting circuit in the curl SUMMARY OF THE INVENTION In the invention of subject invention, a first serial circuit comprisedof a first resistor, a first composite transistor and a first load is connected across a constant current source and a second serial circuit comprised of a second load, a second composite transistor, a second resistor, a third load and a third resistor is connected across a current source. The first resistor and the first composite transistor are connected parallel to the second resistor and the second composite transistor. The resister is connected in the circuit of the second composite transistor. When the voltage across the base electrode and the emitter electrode of the first composite transistor is made substantially equal to the voltage across the base electrode and the emitter electrode of the second composite transistor, an output voltage of a magnitude larger than the magnitude of the voltage drop due to an input current can be obtained across the second resistor and the third resistor.

Therefore, the object of this invention is to obtain a currentvoltage converting circuit which is capable of supplying current to the above loads simultaneously.

Another object of this invention is to obtain a current-voltage converting circuit which is capable of getting a voltage output larger than the voltage drop due to the input current.

The current-voltage converting circuit of this invention can be used also as a current converting circuit.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 through 4 are the connection diagrams showing the electric current converting circuits which are the basis for the current-voltage converting circuit of this invention and variations of the basic circuits; and

FIG. is a connection diagram showing an embodiment of the current-voltage converting circuit of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, the emitter of a PNP-type transistor Q, is connected to a terminal 1 and the base of an NPN-type transistor Q, through a resistor R, and the emitter of the transistor 0, is connected to a terminal 4 and the base of the transistor Q through a resistor R The collector of the transistor Q, is connected to the negative terminal of a constant current source 11 and the negative terminal of a power source E through a terminal 2 and a load or an operational circuit 2,, and the positive terminal of constant current source 1 1 is connected to terminal 1.

The collector of the transistor 0 is connected to the positive terminal of a power source E through a terminal 3 and a load or an operational circuit Z and the negative terminal of the power source E, is connected to the positive terminal of a power source E and a terminal of a load or an operational circuit Z;. The other terminal of the load 2;, is connected to terminal 4 and the joint between the emitter of the transistor Q and the resistor R, forms a terminal 5.

The circuit surrounded by terminals 1, 2, 3 and 4 is named a four-terminal network N. The resistors R and R perform the function to determine the conversion characteristics.

In the circuit of FIG. I, if constant current source 11 generates a current I in the direction shown in the FIG. a voltage V across terminals 1 and 4 is represented by V: I1R1 bel where, R resistance of resistor R Vbei=voltage across base and emitter of transistor Q The transistors 0 and Q have both high gains and the base current is small compared with the collector current; and therefore it is possible to assume that the collector current of the transistor O is equal to the current I If a current supplied from the battery E, to the circuit consisting of the load Z the transistor 0;, the resistor R, and the load Z is represented by a current I similarly the voltage V across terminals 1 and 4 is shown by the following formula.

As it is possible to make the difference between the voltages V and V extremely small, the following relation can be obtained.

I1R1=I2Rz 7 By changing the above equation, it is obtained that Q5 [P II The above equation means that the current I which is obtained by multiplying the constant current I, flowing through the load Z, by the multiplication factor R /R flows through the loads Z and Z The direction containing the base-emitter junction of the transistors Q and Q is arranged in such a direction that the above voltages V and V compensate each other against the heat of their own generation and the variations of ambient temperature. Consequently, the variations of the voltages V and V due to the change of temperature cancel each other and no error will take place in the circuit.

Thus the connection of two transistors of mutually different polarities makes it possible to reduce the conversion errors compared with the case where only one transistor is used.

As stated above, from across terminals 1 and 4 and from across terminals 5 and 4 can be taken out respectively different voltage outputs 1 R V and I R Instead of the transistors Q and Q2, if composite transistor circuits consisting of a combination of two or more transistors are employed, the conversion accuracy can be improved as the input impedance becomes high and the current amplification factor increases. In addition, as it is possible to make the collector current small in the first stage of the composite transistor circuit, the compensation for the voltage across the base and emitter against the self-generated heat and ambient temperature variation will be extremely improved.

FIG. 2 shows the method to connect the various components in case the polarities of constant current power source 11 in FIG. 1 are reversed.

FIG. 3 shows a connection diagram in case the power source E is inserted between terminal 2 and the load Z, in FIG. 1. This type of connection is employed when it is more desirable to supply power separately from an inverter as the power source E in such a common direct current power source system as impresses a direct current 24 v. voltage to individual instruments.

FIG. 4 shows an arrangement where loads Z and Z; are connected in parallel in addition between terminals 4 and 5 in FIG. 1.

FIG. 5 shows arrangements where composite transistor circuits Q11 and Q are used respectively in place of the transistors Q and Q in the four-terminal network of FIG. 1.

The composite transistor circuits Q 1 and Q are composed of transistors Qiu and Q11; and transistors Qm and Q respectively; and the collector currents of these composite transistor circuits shall be represented respectively by I and la. The collector current consists of a collector current i of the transistor Q12] and a collector current i of the transistor Q12 When the current amplification factor of the transistor Q is expressed by B, the following relation can be obtained between the currents i and i From this equation can be obtained the current i; as shown below:

As this current is equal to Bi the following equation can be obtained:

The above equation can be changed as follows:

From the above equations, 15 can be obtained as follows:

If this formula is transformed by using the input current I it is obtained that This means that by suitably selecting the magnitude of the resistors R and R it is possible to obtain across output terminals 4 and 8 a voltage output larger than the voltage drop R due to the input current I We claim:

1. In an electric current converting circuit comprised of a pair of transistors having mutually different polarities, a pair of resistors connecting the emitters of the respective transistors to the bases of the other transistors, a constant current power source and a first load connected in series with a circuit composed of one of the transistors and one of the resistors, a second load connected together with a current power source and a third load in series with a circuit composed of the other of the transistors and the other of the resistors, and a separate current power source connecting the first load to the third load, characterized in that:

said two transistors are composed of composite transistor circuits; and

a resistor is provided in series with the collector of one of the transistors in one circuit of the pair of said composite transistor circuits thereby to obtain a voltage output from a circuit containing said resistor. 

